Radio communication system searching method

ABSTRACT

A radio communication system searching method for a portable telephone terminal for selecting, when a plurality of radio communication systems having different carrier frequencies are present in a same area, a suitable one of the radio communication systems. The searching method is improved in that radio communication systems can be searched in order beginning with a radio communication system which is the most advantageous to the user to eliminate the problems of a disorder of company types of radio communication systems and system selection involved in adjacent systems of a same company type. After preferential order numbers of a plurality of radio communication systems are registered into the portable telephone terminal, a home radio communication system of a predetermined frequency with which the portable telephone terminal is under contract is first searched, and then, when the home radio communication system has not been searched out successfully, the remaining radio communication systems are successively searched in accordance with the preferential order numbers registered in advance in the portable telephone terminal.

This application is a continuation of application Ser. No. 08/578,784,filed Dec. 26, 1995, now abandoned, which is a continuation ofapplication Ser. No. 08/098,817, filed Jul. 29, 1993, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to a radio communication system searching methodfor a portable telephone terminal for selecting, when a plurality ofradio communication systems having different carrier frequencies arepresent in a same area, a suitable one of the radio communicationsystems.

In radio communication systems for portable telephone terminals(including mobile telephone terminals) of the AMPS (Advanced MobilePhone System) system adopted in North America, Australia and so forth,normally two different types of radio communication systems havingdifferent carrier frequencies are used in a same area so that variousservices by the two systems are available in the area. The two types ofradio communication systems are generally classified from each other andmanaged depending upon whether the enterprise which makes the body ofmanagement is a radio company or a main line company. In the followingdescription, a radio communication system managed by a radio companywill be hereinafter referred to as a radio company system, and a radiocommunication system managed by a main line company will be hereinafterreferred to as a main line company system.

The two types of systems will be described in detail below withreference to FIG. 6. In FIG. 6, a radio company system is arranged ineach of areas defined by broken lines while a main line company systemis arranged in each of areas defined by solid lines. In particular, aradio company system managed by a company A is arranged in an area 101;a main line company system managed by another company B is arranged inanother area 102 which is a substantially same area as the area 101;another radio company system managed by the company A is arranged in afurther area 103 which is different and spaced away from the area 101;another main line company system managed by a further company C isarranged in a still further area 104 which is a substantially same areaas the area 103; a further radio company system managed by a stillfurther company D is arranged in a yet further area 105 which isdifferent and spaced away from the areas 101 and 103; and a further mainline company system managed by a yet further company E is arranged in ayet further area 106 which is a substantially same area as the area 105.

When the systems are managed in such a manner as shown in FIG. 6, if aparticular user of a portable telephone terminal executes a contractwith the radio company system managed by the company A in the area 101,then the radio company system arranged in the area 101 makes a homesystem to the portable telephone terminal user. While the main linecompany system arranged in the substantially same area 102 and managedby the company B is present in the area 101 since the main line companysystem of the company B is a system outside of the contract to the userwho is under contract with the radio company system of the company A,naturally the charge for usage of the main line company system is ratherhigh.

By the way, when the user which is under contract with the radio companysystem of the company A in the area 101 moves from within the area 101to any one of the other areas 103 to 106, any one of these systems isoutside the contract to the user. However, it is supposed that, as seenfrom FIG. 6, there may possibly be the same company as the particularcompany which manages the radio company system with which the user isunder contract such as, for example, the company A which manages theradio company system in the area 103, or an affiliated company of theparticular company such as, for example, the company D which manages theradio company system in the area 105.

While the system which is managed by such company is not the home systemto the user, the user can use the system at a rather lower charge thanthe charge in ordinary roaming (to access a system other than the systemwith which the user is under contract, that is, a main line companysystem when the user is under contract with a radio company system, or aradio company system when the user is under contract with a main linecompany system). Also the charge system for users under contract with amain line company system is substantially similar to that for the userof the radio company system described above.

Accordingly, where the management areas of the systems are constructedas seen in FIG. 6, a portable telephone terminal of a user undercontract with a radio company system is only required to have a functionof preferentially searching a radio company system or of searching onlya radio company system while a telephone terminal of another user undercontract with a main line company system is only required to have afunction of preferentially searching a main line company system or ofsearching only a main line company system.

In short, since the management area configuration of the systems issystematic as seen from FIG. 6, a portable telephone terminal is onlyrequired to preferentially search a radio communication system as withwhich the user is under contract or of searching only such radiocommunication system can be set by operation of the user itself (forexample, by operation of keys). More specifically, if setting forpreferentially searching a radio communication system with which theuser is under contract is performed once, then a system favorable to theuser can always be selected without modifying the setting once more.

In recent years, however, as the demand for portable telephonesincreases, the utilization areas of radio communication systems expandand also the number of radio communication systems continues toincrease. Also excessive competition among radio communication systemsis increasing.

Also, due to an influence of such expansion and increase of andexcessive competition among radio communication systems, theclassification of radio communication systems between a radio companysystem and a main line company system is disordered, and such a form(refer to FIG. 7 which will be hereinafter described) that a sameenterprise manages, in an area, a radio communication system of the samecarrier frequency as that of the radio company system described above,but manages, in another area, another radio communication system of thesame carrier frequency as that of the main line company system describedabove occurs. The function of searching a radio communication systemprovided for conventional telephone terminals cannot cope with thesituation.

Therefore, it is desired that, while a user itself understands thearrangement of radio communication systems, it can make use of afunction of selecting a portable telephone terminal to set and modifycriteria for a search in accordance with a position wherein the portabletelephone terminal is used.

Further, if radio communication systems of the same company type areemployed in adjacent areas, then three or more radio communicationsystems may be present as a result of overlapping of such systems in aregion in which only two radio communication systems have been presenttill then.

In such a situation just described, since a portable telephone terminalof the AMPS specification preferentially searches and accesses a radiocommunication system which is highest in intensity in radio waves(electric field), depending upon the condition of the radio waves, theuser may not possibly access a radio communication system best to theuser (in short, a radio communication system which is the mostadvantageous to the user in terms of the charge for using). In the worstcase, even if the user is in the area under contract (at home), itcannot access even the home system.

For example, the situation wherein radio communication systems of thesame company type are present in adjacent areas and a same enterprisemanages radio communication systems of different company types and thesituation wherein a user cannot access its home system while it is in anarea of the home system will be described in more detail with referenceto FIG. 7. It is to be noted that, also in FIG. 7, any region defined bya broken line is an area in which a radio company system isincorporated, and any region defined by a solid line is an area in whicha main line company system is incorporated.

Referring to FIG. 7, a radio company system managed by a company F isarranged in an area 201; another radio company system managed by anothercompany G is arranged in another area 202 adjacent to the area 201; afurther radio company system managed by a further company H is arrangedin a further area 203 adjacent to the area 202; a still further radiocompany system managed by a still further company I is arranged in astill further area 204 adjacent to the areas 202 and 203; a main linecompany system managed by the company I is arranged in a yet furtherarea 205 which is substantially the same as the area 201; another mainline company system managed by the company F is arranged in a yetfurther area 206 which is substantially the same as the area 202: and afurther main line company system managed by a yet further company J isarranged in a yet further area 207 which almost overlaps with the area203.

It is assumed that, where the systems are managed as seen in FIG. 7, auser of a portable telephone terminal who is, for example, undercontract with the radio company system managed by the company F in theregion 201 accesses at a position P substantially on the boundarybetween the areas 201 and 202 shown in FIG. 7. In this instance, at theposition P, not only the radio company system managed by the company Fbut also the radio company system managed by the company G (area 202)and the main line company system managed by the company I (area 205) arepresent in an overlapping relationship. Here, it naturally is the bestchoice, in short, the most advantageous in terms of the charge forusing, to the user whose home system is the radio communication systemof the area 201 to search and access the radio communication system ofthe area 201 which is the home system of the user.

However, since a portable telephone terminal of the AMPS specificationpreferentially searches and accesses that radio communication systemwhich is highest in intensity of radio waves as described above, even ifthe radio communication system of the company type with which the useris under contract (in this instance, the radio company system) ispreferentially searched, radio waves of the radio company system managedby the company G in the area 202 may possibly be more intense, dependingupon the condition of radio waves, than radio waves of the radio companysystem managed by the company F in the area 201 which is the home systemof the user. Thus, while the user is in the area 201 in which the homesystem of it is arranged, it may search and access the radio companysystem managed by the company G which is not the home system of theuser.

Recently, also, a radio communication system with which, even when thisis a roam system (a radio communication system of a different companytype from that (carrier frequency) of the radio communication systemwith which the user is under contract), a service is available at a lowcharge similar to that of the home system has been provided as a resultof the intensification of the competition for acquisition of users, andrepletion of a radio communication system searching function on theportable telephone terminal side is demanded earnestly.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a radiocommunication system searching method by which radio communicationsystems can be searched in order beginning with a radio communicationsystem which is the most advantageous to the user, to eliminate theproblems of disorder of company types of radio communication systems andsystem selection involved in adjacent systems of a same company type andenhance economy.

It is another object of the present invention to provide a radiocommunication system searching method wherein the time required tosearch a radio communication system advantageous to a portable telephoneterminal is minimized.

It is a further object of the present invention to provide a radiocommunication system searching method wherein preferential order numbersfor optimum selection can be set arbitrarily to a portable telephoneterminal in accordance with a demand of the user or an area in which theportable telephone terminal is used so that the portable telephoneterminal can cope readily with such a case wherein the user of theportable telephone terminal moves over a wide range.

In order to attain the objects described above, according to an aspectof the present invention, there is provided a radio communication systemsearching method for a portable telephone terminal for selecting, when aplurality of radio communication systems having different carrierfrequencies are present in an overlapping relationship in a same area,one of the radio communication systems, the portable telephone terminalincluding searching means for searching the radio communication systemsand preferential order registration means for registering preferentialorder numbers of the radio communication systems in advance into theportable telephone terminal, the searching method comprising the stepsof searching, by the searching means, a home radio communication systemof a predetermined carrier frequency with which the portable telephoneterminal is under contract, and successively searching, when the homeradio communication system has not been searched out, by the searchingmeans, the remaining radio communication systems in accordance with thepreferential order numbers registered in advance in the portabletelephone terminal by the preferential order registration means.

At the step of successively searching the radio communication systems inaccordance with the preferential order numbers by the searching means,the one of the radio communication systems which has a different carrierfrequency from the predetermined carrier frequency of the home radiocommunication system may be searched preferentially. Or, when thesuccessive searching of the radio communication systems in accordancewith the preferential order numbers by the searching means fails tosearch out a relevant radio communication system, the one of the radiocommunication systems which has the same carrier frequency as thepredetermined carrier frequency of the home radio communication systemmay be searched preferentially by the searching means.

The preferential order numbers may be determined in accordance with thecharge for using of circuits which is advantageous to the portabletelephone terminal.

The preferential order registration means may be provided on a body ofthe portable telephone terminal. In this instance, an operation ofregistering each of the preferential order numbers by the preferentialorder registration means is performed by operating keys provided on theportable telephone terminal to input an ID number and a preferentialorder number of a radio communication system to be registered. Further,the preferential order registration means may include storage means forstoring an ID number of a radio communication system inputted by suchregistering operation in accordance with a preferential order numberinputted subsequently to the ID number.

According to another aspect of the present invention, there is provideda radio communication system searching method for a portable telephoneterminal for selecting, when a plurality of radio communication systemshaving different carrier frequencies are present in an overlappingrelationship and some of the radio communication systems having a samecarrier frequency are managed in adjacent areas by different managementsystem companies, one of the radio communication systems, the portabletelephone terminal including searching means for searching the radiocommunication systems and preferential order registration means forregistering preferential order numbers of the radio communicationsystems in advance into the portable telephone terminal, the searchingmethod comprising the steps of searching, by the searching means, a homeradio communication system of a predetermined carrier frequency in apredetermined area with which the portable telephone terminal is undercontract, and successively searching, when the home radio communicationsystem has not been searched out, by the searching means, the remainingradio communication systems in accordance with the preferential ordernumbers registered in advance in the portable telephone terminal by thepreferential order registration means.

At the step of successively searching the radio communication systems inaccordance with the preferential order numbers by the searching means,the one of the radio communication systems which has a different carrierfrequency from the predetermined carrier frequency of the home radiocommunication system may be searched preferentially. Or, when thesuccessive searching of the radio communication systems in accordancewith the preferential order numbers by the searching means fails tosearch out a relevant radio communication system, the one of the radiocommunication systems which has the same carrier frequency as thepredetermined carrier frequency of the home radio communication systemmay be searched preferentially by the searching means.

The preferential order numbers may be determined in accordance with thecharge for using of circuits which is advantageous to the portabletelephone terminal.

The preferential order registration means may be provided on a body ofthe portable telephone terminal. In this instance, an operation ofregistering each of the preferential order numbers by the preferentialorder registration means is performed by operating keys provided on theportable telephone terminal to input an ID number and a preferentialorder number of a radio communication system to be registered. Further,the preferential order registration means may include storage means forstoring an ID number of a radio communication system inputted by suchregistering operation in accordance with a preferential order numberinputted subsequently to the ID number.

With the radio communication system searching method, after thepreferential order numbers of the radio communication systems areregistered in advance into the portable telephone terminal, the homeradio communication system to the portable telephone terminal issearched first, and then, when the home radio communication system hasnot been searched out successfully the remaining radio communicationsystems are successively searched in accordance with the preferentialorder numbers registered in advance in the portable telephone terminal.Consequently, the radio communication system searching method isadvantageous in that the radio communication systems can be searchedsuccessively in order beginning with the one of the radio communicationsystems which is the most advantageous to the user of the portabletelephone terminal. The problems of a disorder of company types of theradio communication systems and system selection involved in an adjacentarrangement of systems of a same company type can be eliminated, andbesides, the searching system is very superior in economy.

Further, where, at the step of successively searching the radiocommunication systems in accordance with the preferential order numbers,that the one of the radio communication systems which has a differentcarrier frequency from the predetermined carrier frequency of the homeradio communication system is searched preferentially, there is anadvantage in that the time required to search out a radio communicationsystem advantageous to the portable telephone terminal is reducedremarkably. Similarly, when the successive searching of the radiocommunication systems in accordance with the preferential order numbersfails to search out a relevant radio communication system, where thatthe one of the radio communication systems which has the same carrierfrequency as the predetermined carrier frequency of the home radiocommunication system is searched preferentially, similarly the timerequired to search out a radio communication system advantageous to theportable telephone terminal can be reduced remarkably.

Further, where the preferential order numbers are determined inaccordance with the charge for using circuits which are advantageous tothe portable telephone terminal, the radio communication systems aresuccessively searched beginning with the one of them which isadvantageous in terms of the charge, and accordingly, the economicaladvantage is very high.

Furthermore, since the keys provided on the portable telephone terminalcan be operated to input an ID number and a preferential order number ofa radio communication system to be registered and the ID number of theradio communication system can be stored into the storage means of thepreferential order registration means provided on the body of theportable telephone terminal in accordance with the preferential ordernumber of it inputted subsequently to the ID number, optimumpreferential order numbers can be registered arbitrarily into theportable telephone terminal in accordance with a requirement of the userand/or an area in which the portable telephone terminal is used.Consequently, the radio communication system searching method can copereadily with a case wherein the user of the portable telephone terminalmoves over a wide range.

Further objects, features and advantages of the present invention willbecome apparent from the following detailed description when read inconjunction with the accompanying drawings in which like parts orelements are denoted by like reference characters.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart illustrating different steps of operations of aradio communication system searching method according to the presentinvention;

FIG. 2 is a flow chart illustrating the radio communication systemsearching method of the present invention in more detail;

FIG. 3 is a perspective view showing an appearance of a portabletelephone terminal to which the radio communication system searchingmethod of the present invention is applied;

FIG. 4 is a block diagram showing a general construction of the portabletelephone terminal shown in FIG. 3;

FIG. 5 is a block diagram functionally showing a construction for asearching function and a registering function of the portable telephoneterminal shown in FIG. 3;

FIG. 6 is a diagram showing an example of arrangement of managementareas of radio communication systems; and

FIG. 7 is a similar view but showing another example of arrangement ofmanagement areas of radio communication systems.

DESCRIPTION OF THE PREFERRED EMBODIMENT

While a preferred embodiment of the present invention is describedbelow, the radio communication system searching method of the presentembodiment is applied to a case wherein, when radio communicationsystems of two different company types (a radio company system and amain line company system) having different carrier frequencies arepresent in an overlapping relationship and some of the radiocommunication systems (the radio company system and the main linecompany system) having a same carrier frequency are managed in adjacentareas by different management type companies and besides some of theradio communication systems of different company types are managed by asame enterprise similarly as in the arrangement of management areas ofradio communication systems shown in FIG. 7, one of the radiocommunication systems is selected by a portable telephone terminal.

Before the radio communication system searching method of the presentembodiment is described in detail, names of various systems in thepresent embodiment, criteria for determination of a preferential orderin the present embodiment and a system of charges for using (charges forusing of circuits) will be described below.

The present embodiment involves radio communication systems of twocompany types including a radio company system and a main line companysystem having different carrier frequencies as described above, and thetype (predetermined carrier frequency) of a system with which a portabletelephone terminal is under contract will be hereinafter referred to ashome type while the type of any other system than the system with whichthe portable telephone terminal is under contract will be hereinafterreferred to as roam type. In short, to a portable telephone terminalunder contract with a radio company system, the radio company system isa home type system while a main line company system is a roam typesystem. It is assumed here that, in the present embodiment, a radiocompany system is the home type system of the portable telephone.

Further, while a portable telephone terminal normally has a contractwith regard to an area (for example, the area 201 in FIG. 7) togetherwith a type (predetermined carrier frequency) of a radio communicationsystem, the radio communication system of the home type in the contractarea will be hereinafter referred to as home type/home or home system(home radio communication system), and a radio communication system ofthe roam type in the contract area will be hereinafter referred to asroam type/home. Further, a home type in any other area than the contractarea will be hereinafter referred to as home type/roam, and a roam typein any other area than the contract area will be hereinafter referred toas roam type/roam.

Meanwhile, in the present embodiment, by registering radio communicationsystems into two groups of a first system group and a second systemgroup which are classified in accordance with the criteria describedbelow, the radio communication systems are determined to and classifiedinto two preferential order numbers of the first system group which ishigh in preferential order and the second system group which is high inpreferential order next to the first system group. In particular, thecriterion for determination of registration into the first system groupis that the radio communication system is not the home system but asystem from which a communication service is available with the samecharge for using of circuits as the home system due to, for example,cooperation between the management companies of the systems, and thecriterion for determination of registration into the second system groupis that the system is a system (in most cases, a roam type/roam system)from which a communication service is available at a second lowestcharge for using of circuits next to the home system due to, forexample, cooperation between the management companies of the systemssimilarly to the first system group.

As regards a system of charges (high or low in charge) for usage ofcircuits, where the system names mentioned above are used,conventionally the relationship of home system<home type/roamsystem<roam type/home system or roam type/roam system stands. However,where such preferential order numbers as described above, that is, thefirst system group and the second system group, are introduced, in thepresent embodiment, the relationship of home system<first systemgroup<second system group or home type/roam system<roam type/home systemor roam type/roam system stands. In the present embodiment, searchingfor a radio communication system is performed in accordance with theorder hereinafter described so that the best system (system mostadvantageous to the user in terms of the charge for using of circuits)can be selected preferentially irrespective of operation of the user.

Subsequently, the construction of the portable telephone terminal usedin the present embodiment will be described with reference to FIGS. 3 to5.

Referring first to FIG. 3, there is shown an appearance of the portabletelephone terminal. The portable telephone terminal 1 has a keyboardsection 2 on which a ten key set 2 a including a “#” key and an “*” keyfor inputting various information and a function key set 2 b including amode change-over key and a store key for being operated for registrationof a system ID which will be hereinafter described are provided. Theportable telephone terminal 1 further has an antenna 3, a loudspeaker(receiver) 4, a microphone 5, and a display 6 for displaying informationof operation of the keyboard section 2 and so forth thereon.

Referring now to FIG. 4, there is shown a general construction of theportable telephone terminal 1 shown in FIG. 3. The portable telephoneterminal 1 includes a transmitter/receiver 7 connected to the antenna 3for transmitting and receiving radio waves of a radio communicationsystem. The transmitter/receiver 7 functions as means for searching aradio communication system in response to an instruction from a firstmicrocomputer which will be hereinafter described. The portabletelephone terminal 1 further includes a base band circuit 8 fordemodulating and outputting a sound signal received by thetransmitter/receiver 7 during a call to the loudspeaker 4 and formodulating a sound signal received from the microphone 5 to transmit thesame from the transmitter/receiver 7.

The portable telephone terminal 1 further includes a first microcomputer9 for controlling principal functions (communication sequences andvarious user functions) of the portable telephone terminal 1, and asecond microcomputer 10 interposed between the first microcomputer 9 andthe keyboard section 2 and display 6 for controlling man-machineinterface functions (supervision of the keys and display control) of theportable telephone terminal 1.

The portable telephone terminal 1 further includes a ROM (read onlymemory) 11 in which various processing programs (including a processingprogram necessary to execute the searching method in the presentembodiment) for the communication sequences, the user functions and soforth are stored in advance, a RAM (random access memory) 12 serving asa working area for operation of the first microcomputer 9, and an EEPROM(electrically erasable programmable read only memory) 13 serving asstorage means in which dial numbers which are used comparativelyfrequently, a system ID number (which may be hereinafter referred to asSID) of the home system with which the portable telephone terminal 1 isunder contract, SIDs of radio communication systems registered in thefirst system group and the second system group described hereinabove andso forth are stored in advance. It is to be noted that, in FIG. 4, thekeyboard section 2 is shown only including the ten key set 2 a while thefunction key set 2 b is omitted.

Referring now to FIG. 5, there is shown a construction for the searchingfunction and the registering function of the portable telephone terminal1 in the present embodiment. The portable telephone terminal 1 includesSID writing means 14 for writing a SID to be registered, which has beeninputted by manually operating the ten key set 2 a and the function keyset 2 b of the keyboard section 2 of the portable telephone terminal 1in such a manner as hereinafter described, into the EEPROM 13 inaccordance with a preferential order (to which one of the first andsecond system groups the portable telephone terminal 1 is to belong)which is inputted subsequently. The keyboard section 2, the secondmicrocomputer 10, the SID writing means 14 and the EEPROM 13 constitutepreferential order registration means for registering a preferentialorder number of a radio communication system into the portable telephoneterminal 1.

The portable telephone terminal 1 further includes SID reading means 15for reading out SIDs stored in the EEPROM 13 in order of the homesystem, the first system group and the second system group, and SIDcollation means 16 for collating a SID of a radio communication systemreceived from the outside by way of the transmitter/receiver 7 with theSIDs read out by the SID reading means 15 to determine whether or notthe relevant radio communication system has been searched out. Theportable telephone terminal 1 further includes accessing instructionoutputting means 17 for outputting, when it is determined by thecollation means 16 that the relevant radio communication system has beensearched out, an instruction to access the radio communication system.

The radio communication system searching method in the presentembodiment which is performed using the portable telephone terminal 1having such a construction as described above will be described withreference to FIGS. 1 and 2. A general flow of operations of thesearching method of the present embodiment will first be described withreference to FIG. 1.

First, the user of the portable telephone terminal 1 in the presentembodiment classifies the radio communication systems into the firstsystem group and the second system group in terms of preferential ordernumbers in accordance with areas of use of the portable telephoneterminal 1 or some other factors required by the user, and sets the SIDsof the predetermined radio communication systems to the system groups(step A1).

Here, a detailed registering operation will be described. First, themode change-over key of the function key set 2 b of the keyboard 2 ofthe portable telephone terminal 1 will be depressed to change over thedisplaying condition of the display 6 to a registration operation screenfor SIDs, and then required keys of the ten key set 2 a of the keyboardsection 2 of the portable telephone terminal 1 will be successivelydepressed to enter a SID of 5 or 6 figures of the radio communicationsystem to be registered while numerals thus inputted are displayed onthe display 6.

Then, after the SID displayed on the display 6 is confirmed, it isregistered as the first system group into the EEPROM 13 by way of theSID writing means 14, for example, by depressing the “#” key, or it isregistered as the second system group into the EEPROM 13 by way of theSID writing means 14, for example, by depressing the “*” key.

It is to be noted that such SID is determined in advance for each of thetypes (carrier frequencies) of radio communication systems and for eachof areas (management companies) as shown in FIG. 6 and is printed andpublished on a roaming guide book or the like on the market. Thus, theuser of the portable telephone terminal 1 will perform registration of aSID into a suitable system group referring to such a roaming guide bookas described above each time the user moves to a new area or for each ofall areas to which the user may possibly move sooner or later.

After desired SIDs are registered as desired preferential order numbersinto the EEPROM 13 in accordance with the requirement of the user asdescribed above, when the portable telephone terminal 1 is actuallyconnected to the circuit and used, the home system to the portabletelephone terminal 1 is first searched from among all of the availableradio communication systems (step A2).

In particular, the SID of the home system is read out from the EEPROM 13by the SID reading means 15, and the SIDs held by radio waves aredecoded from all of radio waves which can be received by way of thetransmitter/receiver 7. Then, the received SIDs and the SID of the homesystem from the EEPROM 13 are collated with each other by the SIDcollation means 16 to search out the home system to the portabletelephone terminal 1. It is to be noted that, since generally everyradio communication system successively transmits information includingan ID (SID) of the radio communication system and also the portabletelephone terminal 1 holds, in the EEPROM 13 or the like, a SID of thehome system with which it is under contract, such searching for the homesystem as described above can be handled readily only by addition of theSID without departing from a conventional procedure.

When the result of the collation by the SID collation means 16 provescoincidence between the received SID and the SID of the home system andthus proves success in searching out of the home system (YES at stepA3), an accessing instruction is outputted from the accessinginstruction outputting means 17 and the portable telephone terminal 1enters into and thereafter remains in a waiting condition until itaccesses the home system (step A10).

On the contrary when the result of the collation by the SID collationmeans 16 proves the presence of no received SID which coincides with theSID of the home system and hence proves failure in searching out of thehome system (NO at step A3), the first system group from which acommunication service is available at the same charge for using ofcircuits as that of the home system is searched (step A4). Then, whenthe searching of the first system group results in failure (NO at stepA5), the second system group is searched subsequently (step A6).

Also in searching at each of steps A4 and A6, similarly as uponsearching for the home system, SIDs of radio communication systems whichbelong to the first system group or the second system group are read outfrom the EEPROM 13 by the SID reading means 15 while SIDs of radio wavesreceived by way of the transmitter/receiver 7 are decoded, and thereceived SIDs and the SIDs from the EEPROM 13 are collated with eachother by the SID collation means 16 to search out a radio communicationsystem which belongs to the first system group or the second systemgroup.

Then, when a radio communication system of the first system group hasbeen searched out (YES at step A5) or when a radio communication systemof the second system group has been searched out (YES at step A7), anaccessing instruction is outputted from the accessing instructionoutputting means 17 and the portable telephone terminal 1 enters intoand thereafter remains in a waiting condition until it accesses theradio communication system which belongs to the first system group orthe second system group (step A10).

On the contrary, when no radio communication system of any of the firstsystem group and the second system group has been searched out (NO atsteps A5 and A7), searching processing similar to that in the prior artis entered (step A8). In the searching processing. For example, becauseof the reason described in the description of the related art, a radiocommunication system of the home type to the portable telephone terminal1 (here, a radio company system) is searched preferentially. Then, whena radio company system (or in some other case, a main line companysystem) has been searched out as a result of the searching processing atstep A8 (when the judgment at step A9 is YES), an accessing instructionis outputted from the accessing instruction outputting means 17 and theportable telephone terminal 1 enters into and thereafter remains in awaiting condition until it accesses the radio communication system (stepA10).

Subsequently, a searching processing operation in the present embodimentafter desired SIDs have been registered with desired preferential ordernumbers in accordance with the requirements of the user will bedescribed in more detail with reference to FIG. 2.

After the power supply to the portable telephone terminal 1 is turnedon, first the home system to the portable telephone terminal 1 issearched from among all of radio communication systems which can bereceived then (searching processing C1 for the home system). In short,similar processing to that at steps A2 and A3 described above isperformed to determine whether or not the home system has been searchedout successfully (steps B1 and B2).

Here, each searching processing C1 to C3 illustrated in FIG. 2 isdivided into two layers of an initialization portion and a pagingchannel selection (P-CH selection) portion, and determination of thepresence or absence of the home system and success or failure inreception of data are determined in each layer. This is because, wherethe portable telephone terminal 1 is a mobile telephone terminal, theposition of the terminal 1 may possibly vary by a great amount in ashort time, resulting in a great variation of the receiving conditionfrom a radio communication system, and accordingly, the samedetermination is performed twice for the object of confirmation.

When it is determined at steps B1 and B2 that the home system ispresent, the portable telephone terminal 1 enters into a waitingcondition. But, on the contrary, when it is determined at steps B1 andB2 that the home system has not been searched out, the searchingprocessing C1 for the home system is ended, and then, the searchingprocessing C2 for those of roam type systems (main line company systemsin the present embodiment) which belong to the first system group andthen to the second system group is performed.

In this instance, it is considered that the portable telephone terminal1 is present in an area in which it cannot search the home system, thatis in any other area than the area in which the home system is arranged.In such an instance, since a system of the roam type (a main linecompany system in the present embodiment), different from the home type,is in most cases more advantageous in terms of the charge from excessivecompetition among radio communication systems in recent years, in thepresent embodiment, the searching processing C2 is performedpreferentially for a system of the roam type. Consequently, the time forwhich it is required to determine a radio communication system to wait,that is, the time for which the user cannot use the portable telephoneterminal 1, can be minimized.

Then, in the searching processing C2, it is determined whether or notdata have been received from a system of the roam type (steps B3 andB4), and then, when it is determined at both of steps B3 and B4 thatdata have been received, processing similar to that at steps A4 to A7 inFIG. 1 is performed to determine whether or not the received datacorrespond to the first system group from which a communication serviceis available at the same charge for using of circuits as that of thehome system (step B5). Then, when the determination at step B5 is in theaffirmative, the portable telephone terminal 1 enters into a waitingcondition. However when the determination at step B5 is in the negative,it is determined subsequently whether or not the received datacorrespond to the second system group (step B6).

When the determination at step B6 proves that the received datacorrespond to the second system group, the portable telephone terminal 1enters into a waiting condition, but when the received data do notcorrespond to the second system group or when it is determined at stepsB3 and B4 that no data have been received from any system of the roamtype, the searching processing C2 is ended, and then, a system of thehome type is searched preferentially by the searching processing C3.

The searching processing C3 is basically similar to searching processingof the prior art and, from the reason described in the description ofthe related art, preferentially searches a radio communication system ofthe home type to the portable telephone terminal 1.

In the searching processing C3, it is determined first whether or notdata have been received from a system of the home type (steps B7 andB8), and when it is determined at both of steps B7 and B8 that data havebeen received, it is subsequently determined by similar processing tothat at steps A4 to A7 in FIG. 1 whether or not the received datacorrespond to the first system group from which a communication serviceis available at the same charge for using of circuits as that of thehome system (step B9). Then, when the received data correspond to thefirst system group, but on the contrary, when the received data do notcorrespond to the first system group, it is further determined whetheror not the received data correspond to the second system group (stepB10). Then, when the received data correspond to the second systemgroup.

At step B11, it is determined whether or not the received datacorrespond to any one of inhibited systems. Such an inhibited system isregistered in advance in the EEPROM 13 or the like as a system whichwill not be used from the reason that the charge for using of circuitsis extremely high or from some other reason. When it is finallydetermined at step B11 that the received data do not correspond to anyone of the inhibited systems, the portable telephone terminal 1 entersinto a waiting condition.

On the contrary, when it is determined at step B11 that the receiveddata correspond to one of the inhibited systems, or when it isdetermined at step B7 or B8 that no data have been received the subjectfor searching processing is changed over from a radio communicationsystem of the home type to a radio communication system of the roam type(step B12), and then it is determined whether or not data have beenreceived from a radio communication system of the roam type (steps B13and B8). Thereafter, the processing at steps B13 and B8 to B11 isrepeated while changing over between the home type and the roam type isperformed at step B12 until after a suitable radio communication systemis searched out.

In this manner, according to the searching method of the presentembodiment, the system searching function of the portable telephoneterminal 1 required by the user and the system side is expandedsufficiently, and a SID can be registered arbitrarily in accordance witha preferential order number based on the requirement of the user for theportable telephone terminal 1. Accordingly, radio communication systemscan be searched in order preferentially beginning with a radiocommunication system which is the most advantageous to the user, and thesearching method of the present embodiment not only can eliminate adisorder of the company types of radio communication systems but also issuperior in economy.

Further, as described above, since the searching system of the AMPSspecification preferentially searches and accesses radio communicationsystems beginning with a radio communication system of the most intenseradio waves, when a plurality of radio communication systems overlap ina same region due to adjacent arrangements of radio communicationsystems, if the radio waves of the home system are weak, then even ifthe portable telephone terminal 1 is present in the arrangement area ofthe home system, the situation that the home system cannot be accessedarises with the prior art. However, since the home system to theportable telephone terminal 1 is searched out from among all of radiocommunication systems which can be received then as at step A2 in FIG. 1or the searching processing C1 in FIG. 2, such situation as describedabove can be eliminated, and the problem of selection of a systeminvolved in an adjacent arrangement of systems of the same company type.

Further, when the portable telephone terminal 1 is present outside thearrangement area of the home system, since, in most cases, a radiocommunication system of the roam type is comparatively advantageous interms of the charge due to an influence of excessive competition amongdifferent radio communication systems in recent years, there is anadvantage in that the time required to search out a radio communicationsystem which is advantageous in terms of the charge to the portabletelephone terminal 1 can be reduced remarkably by preferentiallysearching a radio communication system of the roam type as seen from thesearching processing C2 In FIG. 2.

It is to be noted that, while the embodiment is described applied to thecase wherein two different kinds of radio communication systems of theradio company type and the main line company type, in short, two kindsof radio communication systems having different carrier frequencies, arepresent in an overlapping condition, the present invention is notlimited to this.

Further, while the embodiment is described such that radio communicationsystems are classified into two types of the first system group and thesecond system group in terms of the preferential order and SIDs ofpredetermined radio communication systems are individually registeredinto the relevant system groups, the method of the present invention isnot limited to this, and the preferential order can be divided intofiner preferential order numbers.

Further, while in the embodiment described above, the method of thepresent invention is applied to such a situation that a plurality ofradio communication systems having different carrier frequencies arepresent in an overlapping relationship and even radio communicationsystems of a same carrier frequency are managed in adjacent areas bydifferent management company types as seen in FIG. 7 depending upon theareas, the method of the present invention is applied similarly as inthe embodiment described above to another situation wherein a pluralityof radio communication systems having different carrier frequencies aremerely present in an overlapping relationship in a same area as seen inFIG. 6 (those radio communication systems of a same carrier frequencywhich are not managed in an adjacent relationship by differentmanagement company types). Also in this instance, similar advantages tothose of the embodiment described above can be attained.

The present invention is not limited to the specifically describedembodiment, and variations and modifications may be made withoutdeparting from the scope of the present invention.

What is claimed is:
 1. A radio communication system searching method fora portable telephone terminal which selects, when a plurality of radiocommunication systems having different carrier frequencies are presentin an overlapping relationship in a common geographical area, one of theradio communication systems, said searching method comprising: searchingthe radio communication systems for a home radio communication system ofa predetermined carrier frequency desired by a user; searching, prior tothe radio communication systems for a home type radio communicationsystem having a common frequency to the home radio communication system,the radio communication systems for a roam type radio communicationsystem having a different frequency from the home radio communicationsystem according to a first predetermined system set, when the homeradio communication system has not been searched out; searching theradio communication systems for said home type radio communicationsystem according to a second predetermined system set, when the roamtype radio communication system has not been searched out; checking theradio communication systems for an inhibited system when the home typeradio communication system has not been searched out; and searchingagain the radio communication systems for the roam type radiocommunication system when the inhibited system has been searched out. 2.A radio communication system searching method for a portable telephoneterminal which selects, when a plurality of radio communication systemhaving different carrier frequencies are present in an overlappingrelationship in a common geographical area, one of the radiocommunication systems, said searching method comprising the steps of:(a) searching the radio communication systems for a home radiocommunication system of a predetermined carrier frequency desired by auser; (b) searching, prior to the radio communication systems for a hometype radio communication system having a common frequency to the homeradio communication system, the radio communication systems for a roamtype radio communication system having a different frequency from thehome radio communication system according to a first predeterminedsystem set, when the home radio communication system has not beensearched out; (c) searching the radio communication systems for saidhome type radio communication system according to a second predeterminedsystem set, when the roam type radio communication system has not beensearched out; and (d) switching between searching the radiocommunications systems for the roam type radio communication system andthe home type radio communication system, each time a previous one ofthe home and roam type radio communications systems and an inhibitedsystem have not been searched out.
 3. A radio communication searchmethod comprising: registering into a portable telephone terminal aplurality of preferred radio communication systems, the preferred radiocommunication systems having an advantageous charge structure; searchingfor presence of a home system; if the home system is not present,searching for presence of one of the registered preferred radiocommunication systems; and if one of the preferred radio communicationsystems is not present, searching for presence of remaining systems,wherein said searching for presence of one of the preferred radiocommunications systems first searches the preferred radio communicationsystem which have a different carrier frequency from a frequency of thehome system first, then searches for presence of one of the preferredradio communication systems which have a same frequency of the homesystem.
 4. The radio communication search method recited in claim 3,further comprising determining preferential order numbers so that ahigher degree of priority is given to a particular radio communicationsystem which requires a lower charge for use.
 5. A radio communicationsearch method comprising: registering into a portable telephone terminala plurality of preferred radio communication systems, the preferredradio communication systems having an advantageous charge structure;searching for presence of a home system; if the home system is notpresent, searching for presence of one of the registered preferred radiocommunication systems; and if one of the preferred radio communicationsystems is not present, searching for presence of remaining systems,wherein said searching for presence of remaining systems first searchesfor a remaining system using a same frequency of the home system.
 6. Aportable telephone comprising: a registering device registering aplurality of preferential order numbers of radio communication systems,the preferential order numbers having an advantageous charge structure;and a searching device searching for radio communication systems,wherein the searching device searches for presence of a home radiocommunication system of a predetermined carrier frequency, if the homeradio communication system of a predetermined carrier frequency is notpresent, then the searching device searches for presence of one of theregistered preferential order numbers, if one of the registeredpreferential order numbers is not present, then the searching devicesearches for presence of remaining communication systems, wherein saidsearching for presence of remaining systems first searches for aremaining system using a same frequency of the home system.
 7. Theportable telephone recited in claim 6, wherein: the registering deviceregisters a first group of preferential numbers having a same charge asthe home radio communication system, and a second group of preferentialnumbers having a higher charge than that of the home communicationsystem, and when the searching device searches for presence ofpreferential order numbers, the searching device searches the firstgroup first and the second group second.
 8. A radio communication searchmethod comprising: registering into a portable telephone terminal aplurality of preferred radio communication systems; searching forpresence of a home system; if the home system is not present, searchingfor presence of one of the preferred radio communication systems; and ifone of the preferred radio communication systems is not present,searching for presence of remaining systems, wherein said searching forpresence of one of the preferred radio communications systems firstsearches the preferred radio communication system which have a differentcarrier frequency from a frequency of the home system first, thensearches for presence of one of the preferred radio communicationsystems which have a same frequency of the home system.
 9. A radiocommunication search method comprising: registering into a portabletelephone terminal a plurality of preferred radio communication systems;searching for presence of a home system; if the home system is notpresent, searching for presence of one of the preferred radiocommunication systems; and if one of the preferred radio communicationsystems is not present, searching for presence of remaining systems,wherein said searching for presence of remaining systems first searchesfor a remaining system using a same frequency of the home system.